The present invention pertains in general to the x-ray mammography apparatus and method. It particularly relates to the detector device utilized with conventional and digital mammography x-ray devices in order to improve the accuracy of the reading and diagnosis.
As the current medical profession battles to find a cure for breast cancer, x-ray mammography is widely utilized for the screening and diagnosis of breast cancer for millions of women throughout the world. With millions of women diagnosed with breast cancer, the ability to detect and diagnose the incidence of breast cancer as early as possible is absolutely essential. The mistakes or failures in detection end up barring the possibility of early treatment for breast cancer in the most effective manner, requiring expensive and significantly more dangerous surgical and other procedures and even causing death for some patients. In addition, the so-called xe2x80x9cfalse positivesxe2x80x9d are very prevalent with current mammography devices and systems, which often translates into unnecessary costs (for biopsy tests, etc.) and patient trauma.
Mammography, which usually means the radiological examination of the human breast, is typically performed with x-ray or other film/screen techniques. The film screen x-ray mammography technique involves directing a beam of x-ray through the breast onto a phosphor screen, which converts each x-ray photon into a number of visible photons that expose a sheet of photosensitive film, which is located in a close proximity to the phosphor, thereby forming a latent image of the x-ray pattern. The photographic film is developed to transform the latent image into a visible analog representation of the x-ray pattern.
While still widely used throughout the word, the film-screen mammography technique is known to have some shortcomings and limitations. For example, one shortcoming of conventional x-ray mammography is that the range of contrast of the photosensitive film is limited and fails to display the entire range of contrast in the examined human breast. Because the gray-level of x-ray film has a sigmoidal response as a function of exposure, it causes some difficulties in differentiating the contrast at the extremes of the exposure range (in the most radiodense and radiolucent areas of the photo image), thereby complicating analysis and diagnosis of soft tissue masses in those areas.
A more precise approach to the diagnosis of breast cancer had been proposed with the advent of digital mammography techniques, where the phosphor and film detector is replaced with a digital image detector, which provides a much wider range of contrast than photosensitive film, and where the contrast response is linear over the entire contrast range. This allows the digital detector of the mammography device to differentiate among very subtle variations in attenuation of x-rays as they pass through the soft tissue of human breast.
As shown in FIG. 1, a typical mammography apparatus 1 that is commonly used today has an x-ray housing 2 that carries an x-ray arrangement 3 (or an x-ray tube), a subject table 4 and a compression mechanism 5, with compression plate 8. A detector cassette 6, with photosensitive film can be inserted into subject table 4 in the horizontal direction. The housing 2 can be mounted on a rotary arm 7 that is rotatably attached to a movable stand (not shown), allowing the x-ray housing to rotate in order to be able to take x-ray measurements from the side. A more detailed description of a conventional x-ray apparatus is given in the U.S. Pat. No. 6,208,708 and U.S. Pat. No. 5,170,419, the disclosure of which is incorporated herein by reference.
It is also known in the art that a detector cassette itself may serve as a subject table, in which case the compression plate 8 presses the examination subject against the upper surface of the cassette holder when the x-ray beam 9 is emitted by the x-ray tube through the subject breast toward the detector cassette.
One significant shortcoming of the typical x-ray mammography devices that are currently utilized and known in the art, which is common to both the film screen x-ray devices and those that utilize digital detectors, is that the shape of the subject table 4 and the detector cassette 8 (or detector plate in digital mammography devices) is always rectangular. Because the human breast, rib cage below the breast and axillia areas are not linear, when the subject breast is compressed between the subject table and the compression plate and the x-ray beams transmitted, detected and imaged, certain portions 11 or 12 at the far corners of the junction of the breast 10, as shown in FIG. 2 are not properly detected and imaged, thereby creating a potential for misdiagnosis or requiring that the diagnostic mammography procedure be repeated, thus, subjecting the individual to additional x-ray exposure and increasing overall cost of mammography procedures in the aggregate. In many cases, the rectangular cassettes (or digital detectors) also fail to properly image the axilla area, and, therefore, fail to detect cancerous growth in that area, putting the patient""s life at risk. If a cassette with a concave curved surface, formed by one arc with one radius, is utilized in a mammography cassette, the curved surface of such cassette would not be able to accommodate left and right curvature of human breast and curvature of the rib cage below the breast. Thus such cassette would not allow a complete x-ray reading and detection of all areas of the human breast under examination, particularly at all points of connection with the rib cage wall and the axilla area. Furthermore, one such curvature would not be capable of accommodating variations in shape of a rib cage and each breast in patient, as well as variations between individuals with substantially different physical characteristics. Thus, it is desirable to provide an x-ray mammography diagnostic apparatus and method that optimize the curvature of one or more sides of the subject table in such a way as to allow to take a more accurate reading of the left and right breast of an individual under examination, taking into account the different curvature of the breast and the rib cage on each side.
Therefore, there is a need for a simple and inexpensive solution to this problem that would allow a more accurate reading, detection and subsequent diagnosis of all areas of the human breast, particularly at all points of connection with the rib cage wall and in the axilla area.
It is further desirable to improve the accuracy of existing x-ray mammography devices and medical diagnoses based upon the images produced by such devices by providing a full and complete reading of all areas of the human breast and by avoiding significant technological modifications and replacement of thousands of existing x-ray mammography devices and the methods of their manufacturing.
It would be further desirable to improve the accuracy of existing x-ray mammography devices that use removable detector cassettes with photosensitive film, as well as those that utilize a stationary (and removable) digital detector plate as a subject table.
Accordingly, it is one object of the present invention to provide an x-ray mammography diagnostic apparatus that utilizes a subject table (which also operates as a detector in digital x-ray devices) with at least one side having a concave curved surface that accommodates curvature of the human breast and curvature of the rib cage below the breast to allow a complete x-ray reading and detection of all areas of the human breast under examination, particularly at all points of connection with the rib cage wall and in the axilla area.
It is another object of the present invention to provide an x-ray mammography diagnostic apparatus that utilizes a subject table with at least one side having a concave curved surface that accommodates curvature of the human breast and curvature of the rib cage below the breast and also accounts for differences in breast and body curvature for different individuals, without sacrificing the accuracy of the x-ray readings and detection. It is a further object of the invention to accommodate the natural curvature of the human body in the axilla area, and to allow for a more complete examination and detection of the axilla for metastases.
It is still another object of the invention to provide an x-ray mammography diagnostic apparatus and method that optimize the curvature of one or more sides of the subject table in such a way as to allow individuals with different body proportions to utilize the same device and method and obtain a complete x-ray reading and detection of all areas of the human breast under examination, particularly at all points of connection with the rib cage wall.
It is a further object of the invention that the improved device and method according to the current invention can be incorporated simply and inexpensively into the design for the existing x-ray mammography devices, without significant and extensive changes to their structure or methods of manufacture.
It is still a further object of the invention to provide a more accurate x-ray mammography diagnostic apparatus and method for use in existing x-ray mammography devices that utilize removable detector cassettes with photosensitive film (with or without subject table), as well as with digital mammography devices that use both stationary and removable digital detector plates as a subject table.
In accordance with these and other objects, the present invention provides an optimum curvature for the subject table, which has the concave curved surface(s) on the side(s) of the subject table in order to accommodate curvature of the human breast and curvature of the rib cage below the breast for a complete x-ray reading and detection of all areas of the human breast under examination, particularly at all points of connection with the rib cage wall, as well as in the axilla area. The curvature of the concave curved surface(s) on adjacent or opposite sides of the subject table (or the detector cassette, if used as a subject table upon which subject""s breast is placed for examination) each is formed by two or more arcs with different radii and is optimized to allow individuals with different body proportions to utilize the same device and method and obtain a complete x-ray reading with a simple mechanical adjustment, such as a rotation or pivoting of the subject table around an axis. The additional concave curved surface on an adjacent or opposite side of the subject table has a different curvature, and is optimized to fit the curvature of the rib cage below the breast for a complete x-ray reading and detection of both breast areas for each patient, which naturally have different curvature, as well as to accommodate curvature of a human breast and rib cage of individuals with different body proportions.
These and other objectives, characteristics and advantages of the present invention will be disclosed in more detail with reference to the attached drawings.